Thermoplastic, predominantly isotactic homo- and copolymers of 1-butene, referred to herein and in the trade as "polybutylene" or "poly-1-butene", are well known materials. Isotactic polybutylene is the subject of U.S. Pat. No. 3,435,017 of Natta et al. The properties and preparation of isotactic polybutylene are described, for example, in "Encyclopedia of Chemical Technology", edited by Kirk-Othmer, 2nd Ed., Supp. Vol., pp. 773-787. Methods for producing such polybutylene are disclsoed, i.e., in U.S. Pat. Nos. 3,362,940 and 3,464,962. Thermoplastic, predominantly isotactic butene-1 homopolymers of the type heretofore described in the literature, e.g., in U.S. Pat. Nos. 3,362,940 and 3,435,017, and produced commercially, are referred to herein as "conventional" polybutylene.
Conventional polybutylene is produced by contact of 1-butene with coordination catalysts which are generally referred to as Ziegler-Natta catalysts. Broadly, such catalysts are the products of contacting a compound of a transitional metal of Group IV of the Periodic Table of Elements or of some other transition metals with an organometallic compound of a metal of Groups I-III. For convenience of reference herein, the transition metal-containing components, which are typically solid, are referred to as "procatalysts", the organometallic compounds as "co-catalysts", and any additional stereoregulating compounds as "selectivity control agents", abbreviated "SCA". Commercial Ziegler-Natta catalysts are designed to be highly stereoregulating in order to produce highly isotactic polyolefins.
Copolymers of butene-1 with various other monomers such as ethylene and propylene are well known. Such copolymers are useful to improve specific properties. For example, butene-1/ethylene copolymers have a better tear strength balance and heat seal. However, such copolymers also typically have a reduced crystallinity since the polymer backbone regularity is reduced. Other comonomers have also been investigated in the past. For example, U.K. Pat. No. 1,101,435 describes copolymers of butene-1 with 1-olefin monomers such as vinyl cyclopropane, vinyl cyclobutane, vinyl cyclopentane, vinyl cyclohexane, 4-vinylcyclohexene, allyl cyclohexene, allyl benzene and styrene. The copolymers described in the U.K. patent have a stable Type II crystalline form and contain 5 or preferably 10% or more by weight of the 1-olefin comonomer. These copolymers, however, are not attractive commercially since they have lower crytallinity than corresponding homopolymers.